The invention pertains to self-cleaning pulleys for belt conveyor systems utilizing helically spiralled belt supporting webs.
Belt conveyors are widely used in the bulk handling of material which may consist of a plurality of hard particles such as stones, rocks, coal and the like. A typical belt conveyor used in the stone and gravel processing art, for instance, would include a motor driven upper drive pulley, a lower idler or tail pulley, and a flexible belt passing over the drive and tail pulleys usually supported intermediate the pulleys by a belt guide or auxiliary rollers which permit the conveyor to form a concave configuration to maintain the material upon the belt.
Such conveyors are usually inclined at a relatively steep angle to the horizontal and due to the vibration of the conveyor and the movement of the rock and gravel particles thereon it is not unusual for rocks and stones to fall from the conveyor at a point above the tail pulley. Such matter falling from the conveyor will often engage the inner sides of the return portion of the conveyor belt which is travelling downwardly toward the tail pulley, or the particle may fall directly into the region of the belt conveyor at the tail pulley, and in such instances the particle may become wedged between a conventional tail pulley surface and the belt. The presence of the particles between the pulley and the belt will stress the belt at a localized point often cutting or ripping the belt, and may possibly damage the pulley. Additionally, such an occurrence may cause misalignment of the belt on the pulley causing the belt to be thrown.
The aforementioned problems can be partially controlled by utilizing shields and pulley baffles, but such devices are troublesome and require constant maintenance and adjustment, and are easily damaged.
Another approach to solving the aforementioned problem has been the use of self-cleaning pulleys utilizing helical webs spiralled in opposite directions from the central region of the pulley wherein foreign matter received within the pulley is conveyed from the pulley ends, and such devices, while patented, have not achieved commercial success. Such self-cleaning pulleys are shown in U.S. Pat. Nos. 2,886,168, Calder, and 3,626,773, Loeffler, and British Pat. No. 810,804. However, such patented devices have the disadvantage of only supporting the conveyor belt at a single point at any axial location on the pulley resulting in high conveyor belt loads at the location of pulley engagement therewith, and such patented devices do not provide adequate support of the belt conveyor at the pulley central region and ends.